I love time lapse stuff, and I've been practicing the art for about 12 years now...
First off, what kind of camera will you be using? Still, video, HD? This matters alot now...
I've done them with HUGE still frames, and have gotten some great stuff, using "Pocket Wizards" as my intervalometer. When I did TLs with video, I used Beta and Digibeta... since they don't have intervalometer, I just "rolled" constantly for sometimes HOURS and then used a Quantel Edit Box to make my speed adjustments.
Now that the NEW HD cameras have built in intervalometers, life is easy! Decide how fast you want/need the time lapse to move. The LONGER the interval between frames, the FASTER the time-lapse will look in the end. For example if you shot clouds at 1 frame every 20 seconds, versus 1 frame every second, the first TL will move MUCH faster. There is a GREAT time-lapse calculator on my friend Doug Jensen's website!
http://vortexmedia.com/TIME.html Doug is SO awesome, he's taken all of the guess work in the terms of "time" out of it for you... check it out, he has two versions... one is "how long will it take to shoot 10 seconds in 24p a 1 frame every second?" That's the version I use most... I often dial up his website on my phone and then roll! (I usually need to know how long I have to stand there! :) )
If clouds are rolling by faster, or people are in the shot, perhaps the longer frame rates won't look "right..."
How do you fix that? Well, that's easy! If you are fortunate enough to have a camera with "frame accumulation" like the ENTIRE XD CAM HD line, by Sony (including the EX cameras!) Dial in the frame accumulation. This is similar to "slow shutter." What happens is that the camera will "mimic" a longer shutter period, allowing for some "blur" in your shot. This will help SMOOTH out your time-lapse. I use at least 4 frames on EVERYTHING, even my 1 frame every 1 second time lapses!
None of that was your REAL question... but I thought it was a good primer. The other post had great information. I've shot time-lapses all over the board, and tried a little of everything... THESE DAYS, I prefer using auto iris... HOWEVER, I live in Arizona! We have VERY brightly lit days, which means I have to dial in serious Neutral Density filters, often with a mattebox, and NOT just with the camera's built in filters... As the sun goes down, I pull them out... UNLESS I want the shot to "go to black" kind of thing.
I'll agree with the other post that I often COMPOSITE a few shots together to get my "finished" look. So I may shoot my "day" look as one clip... my sunset as three to four clips and my night shot as another... Why? Because I also induce MORE frame accumulation once the sun goes down...
With a backlit cityscape you're in for some trial and error. Do you have a few days to try it a few different ways? I'm afraid the auto iris may not work in your situation. If you do try to do this manually... remember a few things in adjusting your iris... 1) make SMALL adjustments! 2) make your adjustments over an extended period of time! (if you're using an intervalometer, remember your frame rate... 24 frames, 30 frames, etc. equal one second... if you need to OPEN up, say from F4 o 2.8... try to make that "move" over several seconds to help easy the jumpy look; 48, 60 frames, what have you.... think SLOW AND SMOOTH!) 3) If you have that frame accumulation turned on... the iris movement will also be blurred!
There are several different methods that work for people in these situations, just try a few and see what works for you...
Curt Pair
Picture This Productions
Sony ICE Team
F900/F800/F350/PDW700/EX1/EX3/D790/D600
Adobe Premiere Pro CS3 HD/Matrox
Phoenix, AZ
